Article-information display system using electronically controlled tags

ABSTRACT

A product information display system has electronic display tags for displaying pricing and product information for products in stores or warehouses. The electronic display tags are electromagnetically coupled to a conductor. A control circuit is used to generate an information signal which contains a tag address and related data. A modulator circuit modulates an a-c. power signal with the information signal and applies it to the conductor for transmission to the display tags. Each of the display tags is equipped with a coil that is electromagnetically coupled to the conductor for picking up the signals carried by the conductor. A demodulator is used to demodulate the signal picked up by the coil to obtain the original information signal. Each of the display tags is provided with a manually operated switch for initializing the tags with initial addresses transmitted by the conductor. A microprocessor in the electronic tag then compares the address contained in subsequent information signals with the address stored in the tag&#39;s memory. If the addresses match, the microprocessor further processes the information signal for visual display or verification functions.

FIELD OF THE INVENTION

The present invention relates generally to an articleinformation-display system (which can include two-way communication) foruse in facilities having a multitude of different articles. The systemdisplays information for the individual articles and the displays can beupdated from a central location. Where the facility is a store, forexample, the invention is useful for displaying the price and name ofeach product on electronic display tags adjacent the respectiveproducts.

BACKGROUND OF THE INVENTION

There have been a number of proposals to automate retail price displaysby the use of electronic price tags. To the extent such systems replaceprinted price tags, these systems are appealing to store owners becausethey reduce or eliminate the need to reprint and replace item price tagseach time the price of an item is changed. This benefits the retailer byreducing or eliminating: the labor required to replace the price tags;the possibility of human error in replacing the price tags; the time laginvolved in changing prices; and the difficulty in changing a largenumber of prices at once. Perhaps most importantly, such systems havethe ability to overcome price discrepancies between the tag and thecheckout scanners.

Problems have been encountered, however, in providing the requisiteinformation and power to the electronic tags at a reasonable cost. Also,some systems still require printed product description labels on thetags to supplement the electronic tags and thus do not eliminate theproblems they were intended to solve. In systems in which the electronictags are hard wired, installation and removal of the electronic tags isexpensive and impractical. Systems which use exposed wires andconnectors are undesirable because they reduce the system's reliabilityand subject the system to damage from electrostatic discharges, spillageand surface oxides. Other systems lack the ability to verify theaccuracy of the displays and the proper functioning of the electronictags while the system is in operation.

A number of wireless display systems have been proposed which rely oninfrared, acoustic, or radio frequency broadcast for transmission ofproduct information to the display tags. These wireless tags require abattery for powering each tag. Adding a battery to the tag increases thecost of each tag and can make the overall system unaffordable for manyapplications. Moreover, since a single retail establishment oftencontains as many as 20,000 to 50,000 display tags, replacement of thebatteries and reprogramming such a large number of tags istime-consuming and costly. The radiated signals can also be shielded,for example, by steel freezer cases, causing communication "dead spots"in a store. Moreover, disposing of batteries has an adverseenvironmental impact. If there are just 50,000 installations with 20,000tags each, that is a billion batteries that have to be disposed of on aroutine basis, and the labor involved in replacing the batteries andreprogramming at each battery change is costly as well. Effective use ofsuch systems requires a battery management system so that the batteriescan be replaced before failure, or before the quality of the tag' sdisplay diminishes to an unacceptable level. Further, because the tagsin a wireless system generally do not communicate problems to thecomputer, the tags have to be visually monitored to identify problemssuch as bad or faint tags.

Another problem in most previously proposed electronic display tagsystems is that the tags have been relatively thick, causing them toprotrude from the shelf rails on which they are mounted. Protruding tagsare subject to damage by shopping carts, and they can impede themovement of store customers within the aisles. Further, the protrusionof the tags into the aisle invites tampering and can result in theft ofthe electronic tags.

SUMMARY OF THE INVENTION

It is a primary object of the present invention to provide an improvedelectronic display tag system in which the tags require neitherbatteries nor direct electrical contacts, as a result of which the tagscan be economically produced and maintained with a high degree ofreliability.

It is another object of this invention to provide an improved electronicdisplay tag system which is extremely energy-efficient and which can besustained during prolonged power outages without the use of batteries inthe tags, so that there is no need to re-initialize the system after apower outage.

Another important object of this invention is to provide an improvedelectronic display tag system in which each tag is a sealed unit so thatit cannot be damaged by the spillage of products stored adjacent thetags, and so that there are no exposed electrical contacts subject tocorrosion or ESD.

A further object of this invention is to provide an improved electronicdisplay tag system which provides two-way communication between thedisplay tags and the controller or controllers for the tags. A relatedobject is to provide such an improved electronic display tag systemwhich permits continual verification of the accuracy of the displays andthe proper functioning of the various display tags.

Yet another object of this invention is to provide an improvedelectronic display tag system which does not rely on radio frequency(RF) signals or infrared signals and thus is not susceptible to problemsfrom blockage or shielding of such signals or interference from otherequipment using similar frequencies.

A still further object of the invention is to provide an improvedelectronic display tag system which permits the display tags to belocated at any desired position along the lengths of the shelves onwhich the products are located.

Another object of this invention is to provide an improved electronicdisplay tag system which does not produce radiation emission problems.

Still another object of this invention is to provide an improvedelectronic display tag system which can be easily and efficientlyinitialized.

It is also an object of this invention to provide an improved electronicdisplay tag system which deters tampering and reduces the possibility ofdamage by recessing the tags and concealing most other functionalelements.

A further important object of this invention is to provide an improvedelectronic display tag system which permits the display of a variety ofdifferent types of product information such as prices, productdescriptions, unit prices, multilingual information and the like.

Another object is to provide an improved electronic display tag systemwhich is extremely reliable and has a relatively small number of partsso as to provide a high MTBF (Mean Time Between Failure).

A further object is to provide an improved electronic display tag systemwhich does not involve any significant waste disposal problems.

Other objects and advantages of the invention will be apparent from thefollowing detailed description and the accompanying drawings.

In accordance with the present invention, the foregoing objectives arerealized by providing an electronic display tag system which includes amultiplicity of electronic display tags, an electrical power supply forsupplying a-c. power for the multiplicity of the display tags, acontroller circuit for providing information signals for themultiplicity of the display tags, a modulator receiving the power signaland the information signals for modulating the power signal with theinformation signals, at least one electrical conductor connected to themodulator and passing in close proximity to a plurality of theelectronic display tags for carrying the modulated power signal to thedisplay tags, a pick-up coil within each display tag andelectromagnetically coupled to the conductor for receiving the modulatedpower signal, a demodulator within each display tag for demodulating themodulated power signal, and a display circuit within each display tagfor generating a display in response to the information signals derivedfrom the demodulated signal.

In a preferred embodiment, the product information display system isinitialized by initially transmitting information signals for successiveproducts with successive tag addresses, and sequentially initializingindividual display tags via manually operable control means provided oneach tag for accepting a transmitted tag address and the informationsignals transmitted therewith.

A preferred embodiment of the electronic tag includes a resonant circuitcontaining the pick-up coil, and an electronically controllableswitching device in parallel with the resonant circuit for modulatingthe impedance of the tag and thereby modulating the alternating signalin the conductor to produce a sub-harmonic frequency current in theconductor. The impedance modulation may be controlled by manuallyoperable switches on the tags for generating input signals representinginformation to be transmitted from the tag to its area controller, and atag microprocessor responsive to those input signals or signals from thearea controller for controlling the modulation of the tag impedance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a typical layout of part of a retailstore equipped with a product information display system arranged inaccordance with the present invention;

FIG. 2 is a block diagram of a product information display system, alsoin accordance with the present invention;

FIG. 3 is a block diagram of the system controller shown in FIGS. 1 and2;

FIG. 4 is a block diagram of one of the area controllers shown in thesystem of FIG. 2;

FIG. 5 is an illustration of the format of the binary word that is usedfor communication between the area controller and one of the electronicdisplay tags shown in the systems of FIGS. 1 and 2;

FIG. 6 is a schematic diagram of an implementation for the electronicdisplay tag shown in the systems of FIGS. 1 and 2;

FIG. 7 is a schematic diagram of an alternative implementation for theelectronic display tag shown in the systems of FIGS. 1 and 2;

FIGS. 8a, 8b and 8c are flow charts showing how the area controller ofthe systems of FIGS. 1 and 2 can be implemented;

FIGS. 9a, 9b, 9c and 9d are flow charts showing how the display tag ofFIGS. 1 and 2 can be implemented;

FIG. 10 is an enlarged front elevation of an implementation of a displaytag for use in the system of FIGS. 1 and 2;

FIG. 11 is an enlarged front elevation of the liquid crystal displayused in the tag of FIG. 10;

FIG. 12 is an enlarged section of an implementation of the display tagand conductor mounted on a shelf rail; and

FIG. 13 is a front perspective view of the implementation shown in FIG.12;

FIG. 14 is a front elevation of a display tag arrangement for displayracks of the type used to display products in blister packs; and

FIG. 15 is a front elevation of a display tag arrangement for multipleproduct bins in a warehouse.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention has application in a variety ofarticle-information display environments. These environments include,among others, grocery stores, hardware stores, auto-parts stores,warehouses, and other establishments where variable article informationis displayed at remote locations. The present invention is particularlyadvantageous when it is used in a large store where there may be as manyas 50,000 different items of merchandise placed on shelves throughoutthe store, and thousands of prices may change each week. Such anenvironment is typical in a retail grocery store, and it is this contextthat the present invention will be described. This invention is alsoparticularly useful in warehouses containing numerous bins of smallparts that are coded or marked with other types of identifications whichare difficult to read.

FIG. 1 depicts part of a retail store including a product informationdisplay system arranged according to a preferred embodiment of thepresent invention. The system includes a plurality of display tags 20disposed along the front rails 22 of the store's multiple displayshelves 24. The prices, descriptions and/or special information for allthe products are displayed on the front edges of the shelves, near therespective products. Typically, there is a one-to-one correspondencebetween each display tag 20 and a particular item of merchandise.Although certain applications may require a display tag 20 to displayproduct-related information regarding multiple products, e.g., therespective products above and below the display tag 20, preferably eachdisplay tag 20 displays information for only one product.

The information to be displayed at each display tag 20 is provided by asystem controller 28. The system controller 28 communicates with thedisplay tags 20 through a shelf-mounted area controller 31 usingmultiple conductors C₁, C₂ . . . C_(n), each of which forms a large loopto communicate with a large number of display tags 20 in a prescribedarea. Typically a single area controller 31 services at least 1000 tags,and each loop services several hundred tags. Each area controller 31 iscontained in an enclosed housing which is mounted in a relatively hiddenposition on the bottom side of one of the shelves. The system controller28 regularly communicates with the display tags for monitoring andreporting display tag failures to the system user and for identifyingservice inquiries and updating the display information, e.g., with pricechanges.

The display tags serviced by any one of the wire loops are usuallylocated on a number of different shelves. By limiting the length of ahorizontal mn of the conductor C to four feet (a typical modular shelflength), non-contiguous shelf lengths can be accommodated with theconductor C weaving across one four-foot length, below to the underlyingfour-foot length, etc. The bottom shelf, however is typically a singleunit extending along the entire length of an aisle, and thus theconductor C preferably extends continuously along the entire length ofthe bottom shelf.

FIG. 1 also illustrates a communication link 32 between the systemcontroller 28, an in-store computer and check-out scanners (not shown inFIG. 1). This link 32 is also used by the system controller to receiveupdate price information from the store computer (not shown). The samecomputer supplies data to both the tags and the scanners so that a newprice for a particular product is updated in the display tag 20 at thesame time the price is sent to the check-out scanners, thereby ensuringthat the price displayed on the display tag 20 for the product is thesame as the price displayed for and charged to the customer at thecheck-out scanner.

FIG. 2 illustrates the product information display system of FIG. 1 inblock form. The system includes a plurality of area controllers 31coupling the system controller 28 to various sets of display tags 20.Each set of display tags 20 is associated with one of the multiple wireloops C₁ -C_(n) connected to each area controller 31. The areacontrollers 31 communicate with the tags 20 using a conventionalmodulation protocol such as amplitude-shift-keying (ASK), which is abinary form of amplitude modulation. Other communication schemes, suchas frequency shift keying (FSK) or phase modulation, can be used insteadof ASK if desired. Communication between the area controllers 31 and thesystem controller 28 is effected using a conventional serial two-waycommunication protocol, preferably a network interface compatible withthe RS422 or RS485 standard. Each of the area controllers 31 is poweredby a d-c. power supply within the system controller 28.

By controlling the display tags 20 through the area controllers 31,several advantages are realized. For instance, the communication speedbetween the system controller 28 and the display tags 20 is increased(because it is not necessary for the system to talk to each tag), theprocessing power required in the system controller 28 is decreased, anda level of modularity is provided for expanding use of the display tags20. Further, use of the area controllers 31 significantly reduces thecost of the system by avoiding the need for an RS485 type interface ateach tag.

Both the tags and the area controllers store data and with theirinteractive communications check each other as part of the auditing andfailure identification system. There is redundant power back-up with abattery in the system controller and in each area controller. The costof individual tags is reduced because certain of the electronics in thearea controller does not have to be duplicated in thousands of tags, andthere is more flexibility for special display messages.

The system of FIG. 2 also includes an in-store computer 40 whichcommunicates with a remotely located central office 42 using a modem.The in-store computer 40 provides a database of information, receivedfrom the central office 42 (or from a scanner controller), for all themerchandise in the store. The database is used to link each product witha physical-location address, an alpha-numeric (or UPC) description, aprice, and a unit cost and general inventory information. The databasemay be accessed for the check-out scanners 44 as well as the systemcontroller 28. Changes in the database of the in-store computer 40 aregenerally initiated by updates received from the central office, butdatabase changes producing display changes can also be made directly atthe in-store computer 40.

After receiving the product data from the in-store computer 40, thesystem controller 28 selects the desired display information andassociated display tag address, and converts this display informationinto a data stream for transmission to the appropriate area controller31. The area controller 31 then forwards this information to theparticular wire loop C₁ -C_(n) which includes the designated tag 20.

Also associated with the system controller 28 is a printer 46 and abattery back-up unit 48. The printer 46 may be used to make hard copiesof the desired displays, for example on regular or transparent paper,for insertion into a shelf rail at any locations not covered by theelectronic tags 20. The printer can also be used to generate store orsystem reports. The battery back-up unit 48 is used to maintain systemintegrity during periods of power interruption.

As illustrated in FIG. 3, the system controller 28 may be implementedusing a personal computer 28 (such as a 486 or equivalent) containing anumber of network boards configured for serial two-way communicationwith the area controllers 31. Or communication can be accomplished withconventional RS422/RS485 interfaces or equivalent. The system controller28 also contains a conventional hard-drive 62 for programs, protocols,addresses and storage, and power and data distribution circuits 64a,64b, etc. for all the area controllers 31 in the system. Eachdistribution circuit 64 transmits and receives serial data over one setof lines 68 and sends d-c. power over another set of lines 70. Arechargeable 24-volt d-c. battery 72 is used as the power source, withan a-c.-powered battery charger 74 activated as necessary to maintain anadequate charge on the battery 72. The battery 72 is the primary powersource for the area controllers 31, emergency power for the system isalso provided from this battery.

Referring now to FIG. 4, one of the area controllers 31 is shown inexpanded form. Each area controller 31 receives the data from theoutputs of the network boards of the system controller 28 and translatesthe data into an information/power signal that is applied to one of theconductors C₁ -C_(n) for transmission to the display tags. Datatransmission to the tags is typically at 1200 baud using ASK.

Each area controller 31 includes a network interface circuit 80 such asan RS485 transceiver circuit, a microcomputer or microprocessor (MPU)82, a memory 84, and a plurality of transceiver circuits 86, one foreach of the conductors C₁ -C_(n). Using the transceiver circuits, themicroprocessor 82 receives the product data from the network interface80 and determines on which conductor the display tag address resides.The microprocessor 82 then generates an information signal formodulating an a-c. power signal supplied to the selected conductor sothat the information signal will be conveyed to the desired display tag20. In a preferred embodiment, the nominal frequency of the power signalcarried by each of the conductors C₁ -C_(n) is 50 KHz.

Each transceiver circuit 86 in the area controller 31 includes adigital-to-analog converter 88, a voltage-to-current driver circuit 90,and a phase-locked loop (PLL) circuit 92 or equivalent detectorcircuitry. The digital-to-analog converter 88 converts the digitalinformation signal from the microprocessor 82 into analog form.Alternatively, a straight analog communication scheme with an analogoscillator can be used. The resulting analog signal is connected to theinput of the driver circuit 90, which converts the analog voltage into aproportional current for driving the display tags 20 via one end of oneof the conductors C₁ -C_(n). The other end is terminated at ground forthe area controller.

The area controller 31 also includes a transformer 87 whose primary isin series with one of the conductors C₁ -C_(n). The transformer 87produces a secondary voltage proportional to the primary current whichis fed back to the voltage-to-current converter 90 and to the PLL input.The PLL circuit 92 senses the presence or absence of the knownsub-harmonic frequency signal from any of the tags. This signal is thendecoded by the MPU 82. A superheterodyne receiver may be used as analternative to the PLL.

A d-c. to d-c. converter and battery charger 94 is used to charge aback-up battery 96, which provides at least one hour of operating powerto the area controller 31. The charger 94 receives its power from the24-volt d-c. supply 72 in the system controller 28 (FIG. 3). Thus, inthe event of a power failure in the system controller 28, or duringshelf relocation, the area controller 31 is able to provideuninterrupted power and control to the display tags 20 for at least onehour. This period of time should be sufficient to permit repair, and ifmore time is needed the battery 96 can be backed up as needed, or thetags can be put in a sleep mode, as described in more detail below.

As illustrated in FIG. 4, the location of the input end of the conductoralternates between the tag and bottom of vertically adjacent shelves.This causes any radiated signals from the loops on adjacent shelves tocancel each other, so that the overall system does not cause anyradiation emission problems. The alternate phasing of the loops alsoreduces cross-talk between adjacent conductors and reduces thesusceptibility of the system to radiation from other sources.

FIG. 5 illustrates a preferred type of serial communication between oneof the area controllers 31 and the associated display tags 20. Theserial data sent from the area controller to the display tags mayinclude a tag address ("select one tag") or a selected group of tags, an"all tag" command to which all tags respond when they recognize aspecial address, a "load selected" command which includes a particulartag address, a "load subroutine" command which loads a set of data inthe unused portion of a particular tag's memory, a "service inquiry"command to query whether any tags need to communicate with the areacontroller, a "reset" command for resetting a particular tag, a "requestchecksum" command which is responded to by a tag sending a checksumcorresponding to its down-loaded data (this is a price verificationroutine), a "request data" command which invites a tag to send selecteddata to the area controller, or "sleep" or "wake-up" commands whichrespectively remove and apply on-board power to certain circuits foreach tag.

The serial data sent from the display tag to the area controllerincludes requests and responses. An "Ack" response means that the tagreceived the communication from the area controller, and a "Nak"response means that the communication failed. A "Request" is anaffirmative response to a service invitation to send data to the areacontroller, and "Data" is the data sent in response to the areacontroller requesting the data.

FIGS. 6 and 7 illustrate two different embodiments of the display tag20. Common reference numerals are used for common components in the twodiagrams. The differences between the embodiments of FIGS. 6 and 7concern the type of inductor 110 (or 110') utilized and the signalprocessing performed by a rectification circuit 114 (or 114'), a powersupply circuit 116 (or 116'), and a signal conditioning circuit 118 (or118').

Data sent to the display tag 20 via the conductor C is received by thedisplay tag 20 using electromagnetic coupling. A pick-up coil orinductor 110 (or 110') is located close enough to the conductor C tocause the changing electromagnetic field around the conductor C toinduce a corresponding current in the inductor 110. This induced currentprovides the display tag 20 with both the necessary operating power andthe data for the display without requiring any physical contact betweenthe display tag 20 and the conductor C. The inductive coupling of bothpower and information signals to the tags eliminates the need forbatteries in the tags and for physical contacts between the tags and thewire loop. This minimizes the cost of the tags, and also avoids problemscaused by contact corrosion and electrostatic discharges.

The preferred embodiment of the pick-up coil 110 is a single coil with afull wave bridge rectifier as shown in FIG. 6, but if desired twoseparate windings may be used, with one winding connected for datadecoding (or demodulation) and the other winding connected for supplyingpower to the display tag. The pick-up coil in the preferred embodimentcan be implemented by winding 43 turns of #32 enameled wire in a channelmolded into the outer periphery of the tag housing, as described in moredetail below in connection with FIGS. 12 and 13.

A capacitor 112 is connected in parallel with the inductor 110 to form aparallel tuned circuit that is responsive to a particular range offrequencies centered about the carrier frequency transmitted by the areacontroller. This resonant circuit maximizes voltage gain andsignificantly improves coupling efficiency.

In FIG. 6, the current induced in the coil 110 is sent through afull-wave rectifier 114 to provide a positive input to a power supplycircuit 116 and a signal conditioning circuit 118. The output of thevoltage regulator 124, which is connected to a capacitor 126, providesoperating power (V_(cc)) for the display tag 20. The signal conditioningcircuit 118 is preferably a Schmidt buffer which improves the rise andfall times and the signal-to-noise ratio of the signal from the coil110. The circuit 118 can be implemented using a commercially availablebuffer having hysteresis control.

In FIG. 7, the induced current is produced in a pick-up coil formed by acenter-tap inductor 110'. The ends of the inductor 110' are connected toa pair of rectifying diodes 114', 114" to provide a full-wave rectifiedpositive signal for the circuit 118'. The diode 114" can be removed(replaced by a wire) for an operable half-wave rectified signal.

The power supply circuit 116' draws current from the center-tap of theinductor 110' and includes a voltage regulator 124 and a capacitor 126at its output for providing operating power (V_(cc)) for the display tag20. The power supply circuit 116' is connected to common (ground) forreturning current through the diodes 114', 114' to the inductor 110'.

In both FIGS. 6 and 7, the output of the signal conditioning circuit 118or 118' is pulse-extended using a monostable vibrator circuit 142. Theoutput of the circuit 142 is monitored by a microcomputer (CPU) 146 fordemodulating the data. A universal-asynchronous-receiver-transmitter(UART) 144 converts the sequential digital pulses from the circuit 142into parallel format for use by the CPU 146, and vice-versa. Anoscillator 147 provides the operating clock signal for both the UART 144and the CPU 146. A manually adjustable trimming resistor 149 replacesthe normally used crystal or ceramic resonator, but produces a muchlarger variation in oscillator frequency from tag to tag. This variationis compensated for by synchronizing the oscillator frequency to thecarder frequency, thereby permitting the use of an R-C oscillator andeliminating the cost and size of a crystal. In this instance, theoscillator cycles are counted during each half cycle, or multiple, ofthe rectified main primary frequency (50 KHz wave rectified to 100 KHzwave). This count is then used to generate internal frequencies that maybe needed for communications.

Depending on the type of CPU 146 that is used, the buffer 118 (118'),the monostable vibrator circuit 142 and the UART 144 may not berequired, since many microcomputers have input ports which canaccommodate and process analog signals directly. With suchmicrocomputers, the UART-related functions are implemented in software.

The microcomputer (CPU) 146 uses conventionally configured operatingmemory, including ROM 148 and RAM 150, and an LCD display memory 152,154 for maintaining an assigned display set on an LCD display 156 andcommunicating with the area controller 31. The display 156 is preferablydriven using a conventional two-row display driver circuit 158controlled by the CPU 146.

To permit input signals to be manually generated at the tag, a pair ofmembrane switches 166 are accessible on the outside surface of the taghousing. Buffers 168, each having a conventional input pull-up resistoror current source, are connected to the switches 166, and the outputs ofthe buffers 168, are supplied to the CPU 146.

Use of low-power CMOS circuitry is preferred for the tags 20. Thispermits the power draw from the conductor C to be maintained under 25milliwatts per tag. In a preferred embodiment, a custom CMOS integratedcircuit (IC) mounted on the printed circuit board contains all of theelectronics except the display, the tuned circuit, the FET 159, thecapacitor 126 and the switches 166, and requires very little power tooperate.

The display tag 20 can transmit signals to the area controller 31 by animpedance modulation scheme which changes the impedance of the tagcircuit that is inductively coupled to the conductor C, thereby changingthe impedance of the loop formed by the conductor C. This impedancechange is detected by the phase-locked loop 92 in the area controller31. To initiate such an impedance change in a display tag, the UART 144turns on a JFET connected in parallel with the resonant circuit 110,112. The conduction of the JFET 159 shorts the capacitor 112, therebychanging the impedance of the circuit coupled to the conductor C. Thus,by modulating the impedance of the tag circuit by successively turningthe JFET 159 on and off, a signal may be induced in the conductor C at afrequency which is a sub-harmonic of the a-c. power signal which servesas the carrier signal.

To avoid naturally generated noise, the sub-harmonics are preferablygenerated by rendering the JFET 159 conductive during odd-number halfcycles of the a-c. power signal in the wire loop. For example, if theJFET 159 is turned on during only one half cycle out of three successivehalf cycles of the a-c. power signal in the wire loop, the frequency ofthe signal induced in the loop by the tag is 2/3 the frequency of thea-c. power signal. Naturally occurring sub-harmonics do not occur at oddfractions of the primary frequency, and thus will not interfere with thesignal artificially generated by the impedance modulation.

With full wave rectification, the frequency of the induced signal is(2F_(c))/N, where F_(c) is the carrier frequency and N is a positive oddinteger. The half cycle count with full wave rectification is 2F_(c).When the FET is turned on every third half cycle, for example, N is 3and the sub-harmonic is 2/3 F_(c).

In the preferred implementation of the impedance modulation scheme, abit of data is represented by a burst of one or more cycles of theartificially generated sub-harmonic signal. Successive bursts, ofcourse, must be separated by periods of no impedance modulation toenable each separate burst to be detected as a separate bit of data.

To transmit both states of a binary bit of data, i.e., a "0" or a "1",the a-c. power signal can be modulated at either of two differentartificially generated frequencies. For example, a "1" can berepresented by a signal having 2/3 the frequency of the a-c. powersignal, while a "0" is represented by a signal having 2/5 the frequencyof the a-c. power signal.

This impedance modulation technique is a way of transmitting data fromthe tag to the area controller in a manner which is virtually powerless.The only consumed power is that needed to turn the FET on and off.

Signals induced in the wire loop by impedance modulation in a tag aredetected in the phase-locked loop 92 in the transceiver 86 of the areacontroller 31. The area controller's micro-processor 82 then decodesthis information and determines which tag is the source of this signal.The area controller then processes this data for functions controlled bythe area controller such as check sums for price verification or passesinformation onto the system controller 28.

Returning to FIGS. 6 and 7, the microcomputer 146 in the tag includesI/O buffers 160 and capacitors 162 for storing an assigned the bits ofcharges representing display tag address. The microcomputer 146 storesthe down-loaded address for the tag by writing the address to the I/Obuffers 160. The ports on the other side of the buffers 160 areconnected to the capacitors 162. In the event of a power failure, theaddress is preserved by the charge on the capacitors 162 for a certainperiod of time. If desired, alternative means of temporary storage maybe used.

As part of a multi-tiered power-backup system, the battery 96 in thearea controller 31 maintains all the tags serviced by that controller innormal operation for a selected time interval following a power failure.At the end of that time interval, which is determined by the MPU 82 inthe area controller, the MPU 82 generates a signal which causes the CPU146 in each tag to turn off the tag display. All the address and productinformation remains stored in the tag memory, including the capacitors162. This second stage of the power-failure mode of operation iscontinued for a specified period of time after which the data stored ineach tag's RAM 148 and ROM 150 is erased, and only the tag addresses arepreserved by the battery backup in the area controller. When the batteryis exhausted, the capacitors 162 then preserve the addresses as long asthe charge on the capacitors 162 is sustained. In the event a tag isremoved temporarily from a rail, the capacitors 162 will maintain theaddress for a few minutes so that it is not necessary to manuallyreprogram the tag when it is reinstalled, as long as the address ismaintained. This multi-level approach provides extensive safeguards to avariety of power-failure conditions.

Address programming for each tag 20 is accomplished by entering thestart-up mode. The first address and associated product information datais generated by the system controller and fed to the area controllersfor transmission to the display tags. This product information dataappears on all the display tags running in the start-up mode. Aninstaller then manually triggers a membrane switch 166 on the particulardisplay tag which is to be identified by the first address, and which isto display the product information data associated with that address andthe shelf product adjacent to it. When the switch is triggered, the CPU146 captures the address and associated product information data andexits the start-up mode, thereby initiating the normal run mode in thedisplay tag. In the normal run mode, the display tag will continuouslydisplay the product information data which is contained in the memory ofthe display tag until it receives an address which matches its storedaddress, at which time it will update the display in accordance with theinformation data immediately following the received address.

Upon exiting the start-up mode, the display tag sends a confirmationsignal back to the system controller 28 via the conductor C and areacontroller 31 to inform the system controller that the first address hasbeen captured by the appropriate tag. The system controller then sendsthe next address and associated product information data to the displaytags. This new product information data is again displayed on all thetags that remain in the start-up mode. Visual inspection to make surethis adjacent shelf product agrees with the tag displayed informationand manual triggering of successive display tags continues until all thedisplay tags have captured addresses and display data. After any givendisplay tag has captured an address during initialization, the systemcontroller is able to update the information in that tag at any time.

During initial system installation only authorized personnel will haveaccess to the display tag rails. Large retail stores typically havecomplete product location data in their databases, and thus the productsin each area controller zone can be sorted in a sequence that enablesthe installer to walk down the aisle and activate the tags sequentially.This saves a significant amount of time.

As shown in the flow chart of FIG. 8a, for communication between an areacontroller 31 and its tags, the data base for the tags associated withthe area controller is first loaded via the system controller. Block 180of FIG. 8a depicts this first step. After initiating the serialcommunication routines (block 182) and sending the product data forinitializing the first tag (block 184), the MPU in the area controllerdetermines if all tags on the system have been initialized (block 186).If the data has been sent for all the tags, the step of down-loading iscomplete and this routine ends, as depicted at block 188. The initialpass through block 186, however, will lead to the step of block 190 inwhich the MPU broadcasts the information for the next tag associatedwith the area controller. At block 192, the MPU waits for one of thetags to respond. If the response is an "Ack" (block 194), flow proceedsto block 196 where the MPU increments the data buffer for initializingthe address for the next tag and then proceeds back to block 186. If theresponse is not an "Ack" (block 194), flow proceeds to block 198 wherethe MPU determines whether a tag has responded with a "Nak". A "Nak"indicates an error which is handled in block 199, and then flow returnsto block 188. If it is neither an "Ack" nor a "Nak", the system tries toload the tag again until it times out. It then reports the error andproceeds to the next tag. This continues until all the tags areinitialized with the appropriate address and product information.

FIG. 8b illustrates how each area controller operates once the step ofdown-loading is complete. Blocks 200, 202 and 204 respectively depictstarting the normal operation program, phase locking to the 50 KHz powersignal and broadcasting to the tags for a service request.

At block 206, the area controller determines if one of the tags hasresponded to the service request. If there is a response, the requestfor service is handled as shown at block 208. If there is not aresponse, the area controller determines that there is no tag requestingservice and flow proceeds to block 210 where a communication check foreach tag in the system is begun. At block 210, the next tag is selected.At blocks 212, 214 and 216, a cyclic redundancy code (CRC) is requestedfrom this next tag, returned by the tag and analyzed by the areacontroller's MPU to ensure that the tag data is correct and the tag isproperly communicating. To ensure the integrity of the communication,the MPU preferably uses the "Load Subroutine" command to send data tothe tag changing the loaded database. This forces the tag to send back anew CRC, which the area controller checks and verifies.

If proper communication is intact for the selected tag, flow proceeds toblock 218 where the MPU determines whether all the tags have beenserviced. If not flow returns to block 210 for servicing the next tag.If all the tags have been serviced, flow returns to the beginning of theprogram at block 200.

If the CRC is not intact for the selected tag, flow proceeds from block216 to blocks 220 and 222 where the area controller's MPU sends adown-load command and down-loads the initialization data for the tagthat is not properly communicating. From block 222, flow proceeds toblock 224 where the MPU executes another CRC poll, as described above,to ensure that the data was properly received by the tag and that theintegrity is still intact. If the data was properly received, flowproceeds to block 218 to determine if all the tags have been serviced.If the data was not properly received, flow proceeds to blocks 226 and228 where the MPU continues to attempt to get the data to the tag for aperiod of time and then reports the malfunction to the systemcontroller. From block 228, flow returns to block 204 where anotherbroadcast service request is made and the process repeats.

Referring now to FIG. 9a, a flow chart shows how the display tag isprogrammed to initialize the tag with an address and to bring the tag"on-line". This programming mode starts at block 230 and proceeds toblock 232 where the microprocessor in the tag performs a power-onself-test (block 232) involving memory and register checks. At block236, a test is performed to determine if the self-test passed. If not,flow proceeds from block 236 to 234 where the tag reports the error viathe visual display. If the self-test passes, flow proceeds from block236 to block 238, 240 and 242 where UART is initialized and the tag'sclock is adjusted and phase-synchronized to the frequency (50 KHz)sensed on the power signal carried by the conductor. From block 242,flow proceeds to block 244 where the tag temporarily assigns itself tag"00," so that it can receive the "Load All" command from the areacontroller for address initialization.

At block 246, the tag monitors the power signal on the conductor todetermine whether or not the tag has received a data packet. If a packetis received, flow proceeds from block 246 to block 248 where the tagstores the embedded address. Within the packet is the productinformation. From block 248, flow proceeds to blocks 250 and 252 wherethe tag stores the information to be displayed and displays thatinformation on the tag's visual display.

From block 252, flow proceeds to block 254. At block 254, the tagdetermines if the initialization key (switch) has been manually pressed.If not, flow returns to block 246 to continually look for a packettransmitted to this tag. From block 254, flow proceeds to block 256 inresponse to detecting that the initialization key switch has beenmanually pressed.

At block 256, the tag address received within the packet is adopted bythe tag. From block 256, flow proceeds to block 258 where the tag goeson-line by sending an "Ack" communication to the area controller. Atblock 260, the tag is depicted as going on-line. This ends the programmode for initializing the tag.

After initialization, the tag is ready for normal operation, which isdepicted by the flow chart in FIG. 9c. This flow chart begins at block262 and block 268 where the tag immediately begins monitoring theconductor to determine whether an information pack has arrived from thearea controller. If such a packet has arrived, flow proceeds from block268 to block 270 where the tag compares the address embedded in theinformation packet with the address of this tag to determine if thepacket is for this tag. If it is not for this tag, the tag determineswhether the packet represents a broadcast to all tags (such as "STORE ISCLOSING"), as depicted at block 272. If the information packet is forthis tag, flow proceeds from block 270 to blocks 274 and 278 where thetag identifies and executes the necessary action associated with thereceived information packet.

From block 272, flow proceeds to blocks 274 and 278 if the packet isassociated with a broadcast for all tags (the "All tags" command).

From block 268, flow proceeds to block 280 in response to the tagdetermining that a packet has not arrived over the conductor. At block280, the tag performs a test to determine whether a manual buttonsequence has been entered. If such a sequence has not been entered, flowreturns to block 268. If a manual button has been depressed, flowproceeds from block 280 to blocks 282 and 284 where the tag determinesif the sequence is one of the valid sequences. If it is not a validsequence, flow returns to block 268. If it is a valid sequence, flowproceeds from block 284 to block 286 where the command is executed. Fromblock 286, flow proceeds to block 288 where the buffer is cleared andflow returns to block 268.

The sequences are binary numbers entered by depressing membrane switchesrepresenting "0" or "1". Valid sequences include binary sequencescorresponding to requests for: resetting the tag; entering the cursormode (FIG. 9c); verifying the status of the tag and verification codes.Clearing the software buffer which stores the binary digits enteredthrough the switches occurs after a time-out.

Turning now to FIG. 9d, a flow chart for implementing the cursor modefor the display tag is shown. This routine is executed in response to avalid manually-entered sequence.

The cursor mode begins at blocks 290, 292 and 294, where the tag sets upthe display with a cursor position movable by one of the buttons, thescroll button. At blocks 296 and 298, the tag performs a test todetermine whether a scroll button has been depressed. If so, flowproceeds to block 302 where the tag changes (or scrolls through) to thenext cursor code position. From block 302, flow returns to blocks 296and 298 where the tag performs yet another test to determine if thescroll button has been depressed.. This continues with the display codeposition being changed with each depression of the scroll button(switch). When the other switch (the "select button") is depressed, thecurrent cursor position is equated with a package (or function), asindicated at block 306. The current position of the cursor is returnedto the area controller thereby selecting the associated data block. Thearea controller may optionally await a verification to be entered intothe buttons on this tag before acting on selected data.

In summary, one membrane switch is used to select a displayed code andposition the cursor to a selected display character position, and theother switch is used to terminate the cursor mode, selecting the lastposition of the cursor. Such an implementation is ideally used for re,ordering products and alerting the system controller as to the status ofthe product for the associated tag.

From block 306 flow proceeds to block 308 where the tag sends the set ofselected codes to the area controller. At block 310, the tag resets thedisplay.

FIG. 10 illustrates a front view of the tag 20 shown in thepreviously-discussed figures and FIG. 11 shows the details of the faceof the LCD display. The printed circuit board or flex circuit carryingthe electronic components for the tag 20 is concealed within the taghousing 311. The front wall of the housing forms a rectangular aperturefor the LCD display, which includes four seven-segment characters 313, adecimal point 314, an eight-segment units identifier 315, and a "for"annunciator 316 for displaying prices for quantity purchases; an18-character alpha-numeric display 317 (either 5×7 matrix or 14segments) for product descriptions; and a zone 318 with a combination ofcharacters to display cost per unit. A display driver such asFD2258f/FC2258A/FC2258K manufactured by Fuji Electric is used totranslate the parallel data from the memory into the conventional drivesignals for the LCD display. The display is shown to be of the LCD type,but LED's or other types of electronically controlled displays can beused. To seal the display window in the tag housing 311, a clear filmmay be bonded to the front of the tag housing to cover the displaywindow.

FIGS. 12 and 13 illustrate a preferred arrangement for mounting thedisplay tags 20 on a conventional shelf 24 which includes a dependingrail 22 formed as an integral part of the shelf. An auxiliary rail 320is snapped into the shelf rail 22 and extends continuously along thefull length of the shelf for receiving both the display tags 20 and theconductor C.

The auxiliary rail 320 is designed so that the display tag 20 and theconductor C may be snapped into place anywhere along the length of therail. The insulated conductor C is mounted in two channels 321 and 322formed near the top and bottom of the rear wall of the rail 320. The tagis received in a channel formed in the front side of the rail 320. Thetag is recessed inside, and held in place by, a pair of flanges 323 and324 so that the tag does not protrude from the rail. The upper flange323 is flared outwardly at a slight angle so that it can be bentupwardly and outwardly for installation and removal of tags from thefront of the rail. A pair of rearwardly projection flanges 325 and 326hold the rail 320 in place on the shelf rail 22.

As shown in the cross-section of the tag 20 in FIG. 12, the pick-up coil110 is wound around the periphery of the tag housing 311 in a channel328 formed in all four edges of the housing. When the display tag isattached to the rail 320, the coil segments located in the top andbottom sections of the channel 328 are in close proximity to the twosegments of the conductor C on the rear side of the rail 320. Thus, thecoil is electromagnetically coupled to both segments of the conductor C.

As shown in the perspective view of the tag of FIG. 13, a singleconductor C is snapped into the top channel 321 of the rail 320, spansthe length of the store shelf, and then loops to the bottom channel 322of the rail 320 and spans the length of the shelf rail again. Alternatephasing of vertically adjacent shelves, as described above in connectionwith FIG. 4, minimizes cross talk between adjacent conductors along theshelves and avoids any significant radiation of signals from the entiresystem or susceptibility from other sources.

FIG. 14 illustrates a display tag arrangement for products which aredisplayed on racks rather than shelves. This type of display rack iscommonly used for products which are packaged in blister packages. Therack includes multiple rods 330, each of which supports multiplepackages. A package can be removed from the rod by simply sliding thepackage off the forward end of the rod.

In the arrangement of FIG. 14, a rail 320 is mounted directly above therods 330, and contains a separate display tag 20 for each of the rods330. The conductor C is fasten to the rear side of the rail 320 in thesame manner described above in connection with FIGS. 12 and 13.

FIG. 15 illustrates the use of the electronic display tag system ofinvention in a warehouse environment. Many warehouses contain numerousbins containing many different kinds of small articles which aredifficult to identify from the markings on the articles themselves. FIG.15 contains a diagrammatic illustration of four such bins 340. Toidentify the articles in the respective bins, a rail 320 is mounteddirectly beneath each row of bins, and contains a separate display tagfor each bin. Again, the conductor C is mounted on the rear side of eachof the rails 320.

It will be appreciated that various modifications and changes may bemade to the exemplary embodiments illustrated and described hereinwithout departing from the true spirit and scope of the presentinvention, which is set forth in the following claims.

We claim:
 1. A product information display system comprising:multipleshelves and a plurality of electronic display tags mounted on the frontof said shelves; at least one electrical conductor extending along afront portion of each shelf in close proximity to a multiplicity of theelectronic display tags; an area controller for supplying a multiplicityof the display tags with power and data from a single source via saidconductor extending along each shelf, said area controller including ana-c power source for supplying a-c power for a multiplicity of thedisplay tags, a data signal source for supplying data signals for amultiplicity of the display tags. a modulator for modulating said a-cpower with said data signals and supplying said conductor extendingalong each shelf with a single signal containing both power and data; asystem controller for supplying multiple area controllers with datasignals that include information to be displayed on a multiplicity ofsaid display tags, a pick-up coil in each display tag andelectromagnetically coupled to said conductor for receiving the signalcontaining both power and data; each display tag including amicroprocessor, means for powering the microprocessor with power derivedby said pick-up coil from said conductor extending along said shelf, andmeans for supplying the microprocessor with data derived by said pick-upcoil from said conductor extending along said shelf: and a displaycircuit within each display tag for generating a display in response tooutput signals from said microprocessor.
 2. The product informationdisplay system of claim 1 wherein the pick-up coils in the electronicdisplay tags are inductively coupled to said conductor.
 3. The productinformation display system of claim 1 which includes a capactor inparallel with said pick-up coil in each display tag to form a resonantcircuit that enhances the coupling of said conductor to said coil at theresonant frequency of said circuit.
 4. The product information displaysystem of claim 1 wherein said pick-up coil is wound around theperiphery of the display tag.
 5. The product information display systemof claim 1 wherein each data signal includes at least a tag address andproduct information.
 6. The product information display system of claim1 which includes product shelves having front edges and rails extendingalong front edges for receiving said display tags, and said conductorextends along said rails for coupling to said display tags anywherealong said front edges of said shelves.
 7. The product informationdisplay system of claim 1 wherein said conductor is insulated.
 8. Theproduct information display system of claim 1 which includes a rectifierin each tag for converting the a-c power signal picked up by the pick-upcoil to d-c power for said display circuit.
 9. The product informationdisplay system of claim 1 which includes a plurality of rails mounted onthe front edges of product display shelves, each of said rails having afront side and a rear side, said display tags are attached to the frontsides of said rails, and segments of said conductor are attached to therear sides of said rails.
 10. The product information display system ofclaim 1 wherein two spaced parallel segments of said conductor pass inclose proximity to each display tag, and the pick-up coil in eachdisplay tag has portions of the coil in close proximity to said parallelsegments of said conductor.
 11. The product information display systemof claim 1 wherein each of said display tags includes a demodulator fordemodulating signals picked up from said conductor, and means forconverting the power signal picked up from said conductor to a powerinput for the tag display.
 12. The product information display system ofclaim 1 which includes means for controlling said controller toinitially transmit data signals for successive products with successivetag addresses, and each of said display tags includes manually operablecontrol means for initializing the tag by accepting a transmitted tagaddress and the data signals transmitted therewith.
 13. The productinformation display system of claim 1 which includes checkout stationsequipped with scanners for identifying products being purchased fromscannable codes on the products, and a controller supplied with the sameprices included in the product information supplied to said controllercircuit for assigning prices to the products identified by saidscanners.
 14. The electronic display tag of claim 1 which includes aresonant circuit, and said coil forms a part of the resonant circuit.15. The electronic display tag of claim 14 which includes electronicallycontrollable switching means in parallel with said resonant circuit formodulating the impedance of said resonant circuit and thereby modulatingsaid alternating signal in said conductor to produce a data signal insaid conductor at a frequency which is a sub-harmonic of the primaryalternating signal in said conductor.
 16. The electronic display tag ofclaim 15 wherein said controllable switching means is a field effecttransistor.
 17. The electronic display tag of claim 15 which includesmeans for controlling said controllable switching means to producebursts of modulating signals at either of two sub-harmonic frequencies,representing two different states of a binary data bit, so that binaryinformation signals can be generated by the tag.
 18. The electronicdisplay tag of claim 1 which includes manually operable switches forsupplying input signals to said microprocessor.
 19. The productinformation display system of claim 1 wherein said conductor extendsalong said multiple shelves in a pattern such that radiation from aportion of the conductor on one shelf is cancelled by radiation from aportion of the conductor on an adjacent shelf.
 20. The productinformation display system of claim 1 wherein each shelf has two spacedparallel segments of said conductor extending along the front edge ofthe shelf, and each of said display tags includes a pick-up coil withdiametrically opposed portions of the coil in close proximity to saidparallel segments of the conductor.
 21. The product information displaysystem of claim 1 wherein said controller includes a back-up powersource and control means responsive to a power failure to maintain thedisplay tags in normal operation for a first prescribed time intervalfollowing the power failure, and then to turn off the tag displays butretaining all the address and product information in the tag memories,and then to erase all the product information while retaining theaddresses in the tag memories.
 22. The product information displaysystem of claim 1 wherein segments of said conductor extend along thefront edge of each shelf, and each shelf includes a tag rail extendingalong the front edge of the shelf, said rail forming a continuouschannel extending along the front edge of each shelf so that saiddisplay tags can be mounted at any desired location along the front edgeof any shelf.
 23. The product information display system of claim1wherein each electronic display tag comprisesan electromagnetic couplerfor receiving the modulated power signal from said conductor and sendingsignals generated by the electronic display tag; a demodulating circuitconnected to the electromagnetic coupler for demodulating the signalsreceived by the electromagnetic coupler; and a memory for storage of thedemodulated signals.
 24. The product information display system of claim1 whereinsaid conductor and said pick-up coil form a transformer inwhich the primary winding is said conductor and the secondary winding issaid pick-up coil.
 25. The product information display system of claim24 wherein said conductor forms a single continuous primary winding formultiple secondary windings formed by multiple pick-up coils in multipledisplay tags.
 26. The product information display system of claim 1whereinsaid conductor and said pick-up coil form a transformer in whichthe primary winding is said conductor and the secondary winding is saidpick-up coil, said conductor forming a single continuous primary windingfor multiple secondary windings formed by multiple pick-up coils inmultiple display tags.
 27. The product information display system ofclaim 1 which includesa demodulator within each display tag fordemodulating the modulated power signal without amplification, and ananalog-to-digital converter for converting the demodulated signals todigital signals without amplification.
 28. A product information displaysystem for a warehouse having multiple articles stored at multiplelocations throughout the warehouse comprising:a plurality of electronicdisplay tags at the article storage locations; at least one electricalconductor extending along said storage locations in close proximity tothe electronic display tags; an area controller for supplying amultiplicity of the display tags with power and data from a singlesource via said conductor extending along each storage location, saidarea controller including an a-c power source for supplying a-c powerfor a multiplicity of the display tags, a data signal source forsupplying data signals for a multiplicity of the display tags, amodulator for modulating said a-c power with said data signals andsupplying said conductor extending along each storage location with asingle signal containing both power and data; a system controller forsupplying multiple area controllers with data signals that includeinformation to be displayed on a multiplicity of said display tags,wherein each electronic display tag comprises an electromagnetic couplerfor receiving the modulated a-c power from said conductor and sendingsignals generated by the electronic display tag; a demodulating circuitinterfaced to the electromagnetic coupler for demodulating the signalsreceived by the electromagnetic coupler and producing data signalstherefrom; a memory for storage of the data signals; a microprocessorconnected to the memory for processing the data signals; an electronicdisplay connected to the memory for displaying data corresponding to thedata signals stored in said memory; and means for supplying theelectronic display and the microprocessor with power derived by saidelectromagnetic coupler from said conductor, and with data derived bysaid electromagnetic coupler from said conductor.